Can I get arm lipo after a lumpectomy and lymph node surgery?

I am not sure that there will be a way to determine definitively the safety of the procedure in this circumstance.

Hello and thank you for your question.  The
best advice you can receive is from an in-person consultation.  It really depends on your individual anatomy.  Since you have not had any signs of lymphedema, this is a good sign.   The most important aspect is to find a surgeon you are
comfortable with. I recommend that you seek consultation with a qualified
board-certified plastic surgeon who can evaluate you in person.
Best wishes and good luck.
Richard G. Reish, M.D.
Harvard-trained plastic surgeon

You can get arm liposuction but the risks of infection and swelling are much greater.  And you may have had a sentinel node as this is the usual procedure and the sentinel node dissection has a much lower risk profile.